A phrase used to let players in a multiplayer game with an objective know that regular users of that server do not really play the objective and just hang out and frag instead.

No Capping is usually used in CAPture the flag servers but has been known to be used is other game modes as well.

Usually the server and map will be set up to allow for objective to be completed but the majority consensus is No Capping is allowed, as it can be annoying when the map is restarted and usually nobody is really stoping them for capping.